The practice has long been aware that drive trains of vehicles can be designed, utilizing acceleration apparatuses constructed as hydrodynamic torque converters. In order to reduce or to eliminate hydrodynamic loss in the hydrodynamic converter, the concept arose of amplifying the torque converter with a so-called converter-bypass clutch. In the engaged position of a converter-bypass clutch, the situation is, that power transmission in the drive train of a vehicle is diverted around the converter. The transmission of torque is then carried out by way of a connection based on frictional contact, resulting, essentially, in little loss.
Fundamentally, two different system groups (named hereinafter as a “first” system group and a “second” system group) of drive apparatuses, which involve a torque converter and a therewith corresponding converter-bypass clutch, would employ elements and procedures as outlined in the following:
In the case of the first system group, the hydraulic activation of the converter-bypass clutch is integrated in the hydraulic fluid circulation arrangement of the therewith corresponding hydraulic torque converter, such a system is referred to as a “two-line system”. A converter clutch piston of a two-line system activates the converter-bypass clutch. The piston is subjected to hydraulic pressure and its active surface is designed as a flexible disk, the hub of which is rotationally fixed with a turbine of the hydrodynamic torque converter.
Should the converter-bypass clutch be in disengaged state, the converter clutch piston is subjected to pressurizing hydraulic oil flow emerging from the inlet side of the hydrodynamic converter wherein the flow proceeds toward the outlet side of the same. To engage the converter-bypass clutch, it is necessary that an inlet pressure of the hydrodynamic converter be essentially reduced to zero, i.e., shifted thereto. This will yield the result, that an existing static pressure within the hydrodynamic converter would be accordingly depressurized. The converter clutch piston, the movement of which operates the converter-bypass clutch, is coated with a first friction overlay on that side thereof which is remote from the hydrodynamic converter and, during the above operational condition of the hydrodynamic torque converter, this frictional overlay is pushed by a spring arrangement, associated with the converter clutch piston, against the housing of the pump side of the hydrodynamic torque converter.
In order to enhance the capability of the converter-bypass clutch for power transmission and simultaneously to increase the torque carried thereby, an inlet pressure of the same is increased. Raising the level of the inlet pressure of the converter-bypass clutch also increases the pressure of this coated clutch against the housing of the pump side of the hydrodynamic torque converter. Additionally, in a case of an engaged converter-bypass clutch, the converter clutch piston decreases the flow of oil through the hydrodynamic torque converter to a predetermined minimum, such that the converter clutch piston of the converter-bypass clutch essentially assumes the function of a conventional hydraulic check valve.
In order to avoid diminishment of driving comfort, the converter-bypass clutch is advantageously placed in the engaged position especially at a time when the drive train perceives rotational deviations of the internal combustion motor which drives the drive train. Consequently, these deviations cause an audible noise to be heard by the driver. During a period of acceleration, to inhibit this disadvantage, an effort is made to engage as quickly as possible the converter-bypass clutch for the reduction of the hydraulic loss tendency occurring in the hydrodynamic torque converter when the converter-bypass clutch is disengaged.
DE 198 58 541 A1 makes known an electronic-hydraulic control apparatus of an automatically shifted motor vehicle, which includes an arrangement for operating an existing two-line converter designed as a first system group. That is to say, this would be a hydrodynamic torque converter and a corresponding converter by-pass clutch.
DE 10 2005 016 495.1 likewise teaches of a hydraulic control system for a two-line converter which exhibits by-need-only activation of a two-line converter having a solenoid valve with a pressure control valve acting therewith. A control system of the cited invention is assembled with a solenoid valve and a variable pressure control valve operationally connected thereto, wherein the valve disk thereof is designed with pressure reactant surfaces. The result thereof allows a pilot pressure to be controllingly placed in opposition to a spring arrangement.
Additionally, the solenoid valve and the pressure control valve are equipped with a plurality of inlet or outlet control valves (hereinafter designated as “aperture control valves”). These aperture control valves are bound with control lines which supply hydraulic fluid pressure to the torque converter and to the converter bypass clutch. This supplied pressure acts against the remote end faces of the aperture control valve mechanism and the control lines can be subsequently connected with both the torque converter and the converter-bypass clutch. A supply pressure aperture control valve of the solenoid valve, which is subjected to pressure, can be brought into a working connection with an operational pressure aperture control valve of the solenoid valve, which latter aperture control valve. The operational pressure aperture control valve is in communication with the inlet side of the torque converter.
Further, the solenoid valve has a control space, which can be brought into connection with a supply aperture control valve. There is a difference in surface areas between pressure responsive surfaces within the solenoid valve itself; the surfaces being proximal to the control space. This effective difference in surface areas control the flow through the torque converter when the converter-bypass clutch is disengaged.
In ATZ Automobiltechnische Zeitschrift 97 (1995), no. 10, pp. 698 to 706, an article entitled “Electrohydraulic Control and External Shifting of the Automatic Transmission W5A 330/580 of Mercedes Benz” discloses an apparatus for the operation of a hydrodynamic torque converter with a corresponding converter-bypass clutch. The discrete operation of the converter-bypass clutch is based on the hydraulic fluid circulation system of the torque converter. The piston chamber of the converter-bypass clutch is subjected to pressure from a control line, which is separated from the hydraulic fluid through-put zone of the torque converter. The control line uses that pressure which is necessary for the activation of the converter-bypass clutch, while the converter-bypass clutch, as in a two-line converter, is spatially integrated within the housing of the torque converter. Forward drive apparatuses of this kind have been designated in practice as “three-line converters” and have been classified as a second system group.
By a wide margin, the embodiments for drive apparatuses, known to the practice, possess a torque converter and a therewith corresponding converter-bypass clutch. However, in such embodiments, the clutch is hydraulically activated and is placed separately away from the torque converter. This assembly belongs to the second system group, wherein the converter-bypass clutch can be spatially distanced at an optionally selected position in the drive string of a vehicle. The clutch, in this position, for instance, can be employed as a shifting clutch or alternately as a brake within the housing of a transmission apparatus.
The known devices for the operation of drive apparatuses of the first system group and the known devices for the operation of drive apparatuses of the second system group, possess control lines bound with aperture control valves dedicated to valve functions. These control lines, respectively, by way of hydraulic lines of a hydraulic line system serve the hydrodynamic torque converter and the converter-bypass clutch, so that, at appropriate locations, necessary activation pressures can be adjusted in an operationally, reliable manner.
The described known arrangements, however, have system-related disadvantages, in that its operation in the drive apparatuses, which belong to the first system group and its operation in the in the known drive apparatuses for operation in the second system group, are, in general, carried out in different ways, so that the drive apparatuses of one system cannot be operated with apparatuses, which have been provided for the activation of drive apparatuses of the respective other system. This is, in any case, undesirable, since in the area of the transmission control no cost effective, standardized component group can be applied.
With consideration of the above situations, the invention has the purpose of making available an apparatus for the operation of a hydrodynamic torque converter and a therewith corresponding converter-bypass clutch, by way of which both drive apparatuses of the first system as well as the second system can be operated in the same manner. Further, in the invented arrangement, at least partially, one, standardized construction component group, which is independent of a system group can be used.